Handling an Attempt to Resume a Wireless Connection Using a Base Station that Supports a Different Core-Network Type

ABSTRACT

This document describes techniques and devices for handling an attempt to resume a wireless connection using a base station that supports a different core-network type. While in a current resource control state, such as an inactive state 332, a user equipment (UE) 111 or 112 selects a base station 124 with a different core-network type than a previously selected base station 122 or 121. In some cases, this selected base station 124 does not support the current resource control state or does not enable the UE 111 or 112 to transition to a different resource control state, such as a connected state 330. Consequently, if the UE 111 or 112 attempts to perform a procedure that would result in the UE 111 or 112 transitioning to the unsupported resource control state, the procedure may fail and consequently waste network resources or delay communications with the UE 111 or 112.

BACKGROUND

The evolution of wireless communication to Fifth-Generation (5G)standards and technologies provide higher data rates and greatercapacity, with improved reliability and lower latency, which enhancesmobile broadband services. 5G technologies also provide new classes ofservices for vehicular, fixed wireless broadband, and the Internet ofThings (IoT). The specification of the features in the 5G air interfaceis defined as 5G New Radio (5G NR).

To communicate wirelessly with a network, a user equipment (UE) mayestablish a connection to the network using a base station (e.g., aserving cell) that supports a Fifth-Generation core network (5GC), anEvolved Packet Core (EPC), or both. After suspending the connection tothe network, the UE may perform a cell-selection procedure that selectsa different base station. If the selected base station supports adifferent core-network type than the previous base station, however, anattempt to resume the connection to the network using the selected basestation may fail.

SUMMARY

Techniques and apparatuses are described that handle an attempt toresume a connection using a base station that supports a differentcore-network type. In particular, a resource control module of a UEdetermines whether or not a core-network type supported by a currentlyselected base station differs from a core-network type supported by apreviously-selected base station before performing a connection-resumeprocedure. If the core-network types differ, the resource control moduleperforms another action prior to or instead of performing theconnection-resume procedure. As an example action, the resource controlmodule releases the wireless connection to the network, performs aconnection-establishment procedure with the second base station,postpones the connection-resume procedure, or sends a message to anupper layer. In this way, the resource control module takes steps toproactively avoid performing a connection-resume procedure that may faildue to differences in core-network types.

Aspects described below include a method performed by a user equipmentfor handling an attempt to resume a wireless connection using a basestation that supports a different core-network type. The method includesestablishing a wireless connection to a network using a first basestation that supports a first core-network type. The method alsoincludes suspending the wireless connection to the network andperforming a cell-selection procedure that selects a second basestation. The method additionally includes processing system informationreceived from the second base station to determine that the second basestation supports a second core-network type and determining that thesecond core-network type differs from the first core-network type. Themethod further includes detecting a trigger that initiates aconnection-resume procedure. Responsive to detecting the trigger anddetermining that the second core-network type is different, the methodincludes performing one or more operations comprising: releasing thewireless connection to the network; performing aconnection-establishment procedure using the second base station;postponing the connection-resume procedure; or sending a message to anupper layer.

Aspects described below also include a user equipment comprising aradio-frequency transceiver. The UE also includes a processor and memorysystem configured to perform any of the methods described.

Aspects described below also include a system with means for handling anattempt to resume a wireless connection to a network using a basestation that supports a different core-network type by performing atleast one of the following: releasing the connection to the network,performing a connection-establishment procedure using the cell,postponing a connection-resume procedure, or sending a message to anupper layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatuses of and techniques for handling an attempt to resume awireless connection using a base station that supports a differentcore-network type are described with reference to the followingdrawings. The same numbers are used throughout the drawings to referencelike features and components:

FIG. 1 illustrates an example wireless network environment in whichhandling an attempt to resume a wireless connection using a base stationthat supports a different core-network type can be implemented.

FIG. 2 illustrates an example user equipment for handling an attempt toresume a wireless connection using a base station that supports adifferent core-network type.

FIG. 3 illustrates another example environment in which a user equipmentmay attempt to resume a connection using a base station that supports adifferent core-network type.

FIG. 4 illustrates example data and control transactions between a userequipment, a first base station, and a second base station.

FIG. 5 illustrates an example method for handling an attempt to resume awireless connection using a base station that supports a differentcore-network type.

DETAILED DESCRIPTION Overview

This document describes techniques and devices for handling an attemptto resume a wireless connection using a base station that supports adifferent core-network type. While in a current resource control state,such as an inactive state, a user equipment (UE) can select a basestation that supports a different core-network type than a previous basestation. In some cases, this selected base station may not support thecurrent resource control state or may not enable the UE to transition toa different resource control state, such as a connected state.Consequently, if the UE attempts to perform a procedure to transitionthe UE to a different resource control state, the procedure may fail.The failure may result in wasted network resources or delayedcommunications with the UE.

These techniques and devices enable handling an attempt to resume awireless connection using a base station that supports a differentcore-network type. In particular, a resource control module of a UEdetermines whether or not a core-network type supported by a currentlyselected base station differs from a core-network type supported by apreviously-selected base station before performing a connection-resumeprocedure. If the core-network types differ, the resource control moduleperforms another action prior to or instead of performing theconnection-resume procedure. As an example action, the resource controlmodule releases the wireless connection to the network, performs aconnection-establishment procedure with the second base station,postpones the connection-resume procedure, or sends a message to anupper layer. In this way, the resource control module takes steps toproactively avoid performing a connection-resume procedure that may faildue to differences in core-network types.

Example Environment

FIG. 1 illustrates an example environment 100, in which handling anattempt to resume a wireless connection using a base station thatsupports a different core-network type can be implemented. Theenvironment 100 includes multiple UEs 110, illustrated as UE 111, UE112, and UE 113. Each UE 110 communicates with one or more base stations120 (illustrated as base stations 121, 122, 123, and 124) through one ormore wireless communication links 130 (wireless link 130), illustratedas wireless links 131 and 132. Although illustrated as a smartphone, theUE 110 can be implemented as any suitable computing or electronicdevice, such as a mobile communication device, a modem, a cellularphone, a gaming device, a navigation device, a media device, a laptopcomputer, a desktop computer, a tablet computer, a smart appliance, avehicle-based communication system, and the like. The base station 120(e.g., an Evolved Universal Terrestrial Radio Access Network Node B,E-UTRAN Node B, evolved Node B, eNodeB, eNB, Next Generation EvolvedNode B, ng-eNB, Next Generation Node B, gNode B, gNB, or the like) canbe implemented in a macrocell, microcell, small cell, picocell, or thelike, or any combination thereof.

The base stations 120 communicate with the UE 110 using the wirelesslinks 131 and 132, which may be implemented as any suitable type ofwireless link. The wireless link 131 and 132 can include a downlink ofdata and control information communicated from the base stations 120 tothe UE 110, an uplink of other data and control information communicatedfrom the UE 110 to the base stations 120, or both. The wireless links130 include one or more wireless links or bearers implemented using anysuitable communication protocol or standard, or combination ofcommunication protocols or standards such as 3rd Generation PartnershipProject Long-Term Evolution (3GPP LTE), Enhanced Long-Term Evolution(eLTE), Fifth-Generation New Radio (5G NR), Fourth-Generation (4G)standard, and so forth. Multiple wireless links 130 can be aggregated ina carrier aggregation to provide a higher data rate for the UE 110.Multiple wireless links 130 from multiple base stations 120 can beconfigured for Coordinated Multipoint (CoMP) communication with the UE110.

The base stations 120 are collectively a Radio Access Network 140 (RAN,Evolved Universal Terrestrial Radio Access Network, E-UTRAN, 5G NR RANor NR RAN) that each use a Radio Access Technology (RAT). The RANs 140include an NR RAN 141 and an E-UTRAN 142. In FIG. 1, core networks 190include a Fifth-Generation Core (5GC) network 150 (5GC 150) and anEvolved Packet Core (EPC) network 160 (EPC 160), which are differenttypes of core networks. The base stations 121 and 123 in the NR RAN 141are connected to the 5GC 150. The base stations 122 and 124 in theE-UTRAN 142 connect to the EPC 160. Optionally or additionally, the basestation 122 connects to both the 5GC 150 and EPC 160.

The base stations 121 and 123 connect, at 102 and 104 respectively, tothe 5GC 150 using an NG2 interface for control-plane signaling and usingan NG3 interface for user-plane data communications. The base stations122 and 124 connect, at 106 and 108 respectively, to the EPC 160 usingan S1 interface for control-plane signaling and user-plane datacommunications. If the base station 122 connects to both the 5GC 150 andEPC 160, the base station 122 can connect to the 5GC 150 using an NG2interface for control-plane signaling and using an NG3 interface foruser-plane data communications, at 180. In addition to connections tocore networks 190, base stations 120 can communicate with each other.The base stations 121 and 123 communicate using an Xn interface at 112,for instance. The base stations 122 and 124 communicate using an X2interface at 114. The base stations 122 and 123 can communicate using anXn interface at 116 to execute a handover procedure.

The 5GC 150 includes an Access and Mobility Management Function 152 (AMF152) that provides control-plane functions such as registration andauthentication of multiple UE 110, authorization, mobility management,or the like in the 5G NR network. The EPC 160 includes a MobilityManagement Entity 162 (MME 162) that provides control-plane functionssuch as registration and authentication of multiple UE 110,authorization, mobility management, or the like in the E-UTRA network.The AMF 152 and the MME 162 communicate with the base stations 120 inthe RANs 140 and also communicate with multiple UE 110 through the basestations 120.

The UE 110 supports eLTE or a variety of different RATs, such as 5G NRand 4G. Different situations can cause the UE 110 to transition amongdifferent resource control states as determined by the RAT. Exampleresource control states include a connected state in which the UE 110establishes a wireless connection to a network using the base station120, an inactive state in which the UE 110 suspends the wirelessconnection to the network, or an idle state in which the UE 110 releasesthe wireless connection to the network. While in the inactive state, forexample, the UE 110 performs the cell-selection procedure. In somecases, the cell-selection procedure selects a second base station thatsupports a core-network type that is different from the core-networktype supported by the previous cell. As such, the selected base stationmay not support the inactive state or may not enable a wirelessconnection to a network to be resumed from the inactive state through aconnection-resume procedure (e.g., a radio-resource-control (RRC)connection-resume procedure). In general, the connection-resumeprocedure enables the UE 110 to transition from the inactive state tothe connected state and resume the connection to the RAN 140. Componentsof the UE 110 are further described with respect to FIG. 2.

Example Device

FIG. 2 illustrates an example device diagram 200 of the UE 110. The UE110 can include additional functions and interfaces that are omittedfrom FIG. 2 for the sake of clarity. In the depicted configuration, theUE 110 includes antennas 202, a radio-frequency (RF) front end 204 (RFfront end 204), a radio-frequency transceiver, including, for example,an LTE transceiver 206, and/or a 5G NR transceiver 208 for communicatingwith one or more base stations 120 in the RAN 140. The RF front end 204couples or connects the LTE transceiver 206 and the 5G NR transceiver208 to the antennas 202 to facilitate various types of wirelesscommunication. The antennas 202 can include an array of multipleantennas that are configured similar to or differently from each other.The antennas 202 and the RF front end 204 are tuned to one or morefrequency bands defined by the 3GPP LTE and 5G NR communicationstandards and implemented by the LTE transceiver 206 and/or the 5G NRtransceiver 208.

The UE 110 also includes one or more processors 210 and memory systemincluding, for example, computer-readable storage media 212 (CRM 212).The processor 210 can be a single core processor or a multiple coreprocessor composed of a variety of materials, such as silicon,polysilicon, high-K dielectric, copper, and so on. The computer-readablestorage media excludes propagating signals and the CRM 212 includes anysuitable memory or storage device, such as random-access memory (RAM),static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM),read-only memory (ROM), or Flash memory useable to store device data 214of the UE 110. The device data 214 includes user data, multimedia data,beamforming codebooks, applications, and/or an operating system of theUE 110, which are executable by the processor 210 to enable user-planecommunication, control-plane signaling, and user interaction with the UE110.

The CRM 212 also includes a resource control module 216. Alternately oradditionally, the resource control module 216 can be implemented inwhole or part as hardware logic or circuitry integrated with or separatefrom other components of the UE 110. The resource control module 216implements an RRC layer, as described according to the wirelesscommunication standard. The resource control module 216 determines theresource control state (e.g., the connected state, the inactive state,or the idle state) and performs operations according to the resourcecontrol state. Instead of directly performing a connection-resumeprocedure, the resource control module 216 evaluates a core-network typeof a currently selected cell. If the core-network type does not supportthe current resource control state or differs from a previous cell'score-network type, the resource control module 216 performs otheractions prior to or instead of performing the connection-resumeprocedure. The resource control module 216 can at least partiallyimplement handling an attempt to resume a wireless connection using abase station that supports a different core-network type, as furtherdescribed in FIGS. 3-5.

Handling an Attempt to Resume a Wireless Connection Using a Base Stationthat Supports a Different Core-Network Type

FIG. 3 illustrates another example environment 300 in which the UEs 111and 112 move to different geographical locations that are serviced bydifferent base stations 121, 122, and 124 of FIG. 1. In this example,the base station 121 is a gNB and supports the 5GC 150. In contrast, thebase station 124 is an ng-eNB or an eNB that supports the EPC 160. Thebase station 122 is another ng-eNB that supports both the 5GC 150 andEPC 160.

Consider that the UE 111 supports eLTE and is positioned at a firstlocation 310, which is proximate to the base station 122. The UE 111performs a cell-selection procedure that selects the base station 122,establishes a wireless link 132 with the base station 122, and operatesin a connected state 330. After some period of time, the UE 111transitions from the connected state 330 to an inactive state 332. Insome cases, the UE 111 receives a request message from the base station122 (shown in FIG. 4) that directs the UE 111 to transition from theconnected state 330 to the inactive state 332. The request message canbe a radio-resource-control (RRC) connection-release message.

While in the inactive state 332, the UE 111 moves to a second location312, which is proximate to the base station 124. The UE 111 performs asecond cell-selection procedure to select or determine a second basestation. The cell-selection procedure can alternatively be referred toas a cell-reselection procedure, which enables the UE 111 to change orswitch to a different base station 120 within the RAN 140. In thisexample, the UE 111 selects the base station 124, which supports the EPC160 and not the 5GC 150. Consequently, the base station 124 does notsupport the inactive state 332 and does not support a connection-resumeprocedure that enables the UE 111 to transition from the inactive state332 to the connected state 330. Since the currently selected basestation 124 does not support the inactive state 332, a future attempt toperform the connection-resume procedure will fail.

A similar problem occurs if the UE 110 performs an inter-RATcell-selection procedure, as described with respect to UE 112. Considerthat the UE 112 is positioned at a third location 314, which isproximate to the base station 121. The UE 112 performs a cell-selectionprocedure that selects the base station 121, establishes the wirelesslink 131 with the base station 121, and operates in the connected state330. After some time period, the UE 112 transitions from the connectedstate 330 to the inactive state 332, similar to the UE 111.Additionally, the UE 112 moves to a fourth location 316, which isproximate to the base station 124. At the fourth location 316, the UE112 performs a cell-selection procedure that selects the base station124, which supports a different core-network type compared to thecore-network type supported by the base station 121. Since thecore-network type supported by the base station 124 does not support theinactive state 332, a future attempt to perform the connection-resumeprocedure while the base station 124 is selected will fail.

To avoid wasting network resources or delaying communications that couldbe caused by a connection-resume procedure failure, the UE 110 performsother actions prior to or instead of performing the connection-resumeprocedure, as further described in FIG. 4. Although the UEs 111 and 112are described as being in the inactive state 332, these techniques canbe applied to other types of resource control states that may not besupported by the selected base station 120.

FIG. 4 illustrates example data and control transactions 400 between theUE 110, the first base station 121 or 122, and the second base station124. In this example, the first base station 121 or 122 supports a firstcore-network (CN) type 402 and the second base station 124 supports asecond core-network type 404, which differs from the first core-networktype 402. As an example, the first core-network type 402 includes the5GC 150 and the second core-network type 404 includes the EPC 160.

At 405, the first base station 121 or 122 and the UE 110 perform aconnection-establishment procedure, which enables the UE 110 towirelessly connect to the RAN 140 using the base station 121 or 122.

At 410, the UE 110 operates in the connected state 330.

At 415, the first base station 121 or 122 sends a request message 416 tothe UE 110. The request message 416 directs the UE 110 to transitionfrom the connected state 330 to the inactive state 332. In some cases,the request message 416 specifies a duration 418 for which the UE 110operates in the inactive state 332 prior to performing aconnection-resume procedure. An example request message 416 includes theRRC connection-release message, as described above with respect to FIG.3.

At 420, the UE 110 transitions from the connected state 330 to theinactive state 332 and operates in the inactive state 332 according tothe request message 416.

At 425, the UE 110 additionally sets a timer that triggers aconnection-resume procedure upon expiration. In some cases, the UE 110sets a duration of the timer based on a predetermined amount of timethat is specified by the computer-readable storage media 212 of the UE110. Alternatively, the UE 110 sets the duration of the timer accordingto the duration 418 specified by the request message 416.

At 430, the UE 110 performs a cell-selection procedure that selects thesecond base station 124. In some cases, the UE 110 selects the secondbase station 124 instead of the first base station 121 or 122 becausethe UE 110 moved to a new location that is closer to the second basestation 124 (relative to the first base station 121 or 122). As anexample, the UE 110 moves to the second location 312 or the fourthlocation 316 shown in FIG. 3.

At 435, the UE 110 receives system information 436 from the second basestation 124. The system information 436 informs the UE 110 of the secondcore-network type 404 supported by the second base station 124.

At 440, the UE 110 determines that the first core-network type 402supported by the first base station 121 or 122 differs from the secondcore-network type 404 supported by the second base station 124.Consequently, a connection-resume procedure with the selected basestation 124 may fail. The UE 110 can also determine that a futureconnection-resume procedure will fail based on a determination that thesecond core-network type 404 does not support the inactive state 332(e.g., the current resource control state of the UE 110).

At 445, the UE 110 detects a trigger that initiates a connection-resumeprocedure. One example trigger includes an expiration of the timer 446,which was previously set at 425. A second example trigger includes arequest to perform a radio-access-network notification-area (RNA) update447. The RNA update 447 provides a single identity (e.g., a RAN areaidentity, a cell identity, or a Public Land Mobile Network (PLMN)identity) or a list of identities (e.g., a list of cell identities) tothe UE 110. In some situations, the RNA update 447 is triggered if a RANnotification area associated with the selected base station (e.g., thesecond base station 124) differs from the RAN notification areaassociated with the previously-selected base station (e.g., the firstbase station 121 or 122). The system information 436 can provide the RANnotification area associated with the second base station 124 to the UE110. A third example trigger includes a message 448 from an upper layer,which triggers the RNA update 447 or the connection-resume procedure.

At 450, the UE 110 performs one or more operations prior to or insteadof the connection-resume procedure. In particular, when it is determinedthat the first core-network type 402 differs from the secondcore-network type 404 and a trigger occurred, the UE 110 releases thewireless connection to the RAN 140 (e.g., transitions to the idlestate), performs a connection-establishment procedure with the basestation 124, postpones the connection-resume procedure, and/or sends amessage to an upper layer, as further described with respect to FIG. 5.By determining that the first core-network type 402 differs from thesecond core-network type 404 at 440, the UE 110 can take action to avoidattempting a connection-resume procedure that wastes network resourcesor delays communications.

Example Method

FIG. 5 depicts an example method 500 for handling an attempt to resume awireless connection using a base station that supports a differentcore-network type. Method 500 is shown as a set of operations (or acts)performed but not necessarily limited to the order or combinations inwhich the operations are illustrated. Further, any of one or more of theoperations may be repeated, combined, reorganized, skipped, or linked toprovide a wide array of additional and/or alternate methods. In portionsof the following discussion, reference may be made to environment 100 ofFIG. 1 or 300 of FIG. 3 and entities detailed in FIG. 2, reference towhich is made for example only. The techniques are not limited toperformance by one entity or multiple entities operating on one device.

At 502, a UE establishes a wireless connection to a network using afirst base station that supports a first core-network type. For example,the UE 110 establishes a wireless link 130 to the RAN 140 of FIG. 1using the base station 120, as shown in FIG. 1. In particular, the UE110 performs a connection-establishment procedure (shown in FIG. 4) asspecified by the wireless communication standard. The UE 110 alsodetermines that the base station 122 supports the first core-networktype 402, such as the 5GC 150, based on system information provided bythe base station 120. In FIG. 3, the UE 111 establishes a wireless link132 to the RAN 142 using the base station 122, which is implemented as ang-eNB that supports both the 5GC 150 and the EPC 160. Additionally, oralternatively, the UE 112 establishes a wireless link 131 to the RAN 141using the base station 121, which is implemented as a gNB that supportsthe 5GC 150.

At 504, the UE suspends the wireless connection to the network. Forexample, the UE 110 suspends the connection to the RAN 140. In somecases, the UE 110 suspends the connection responsive to receiving therequest message 416 of FIG. 4 (e.g., an RRC connection-release message)from the base station 120. The request message directs the UE 110 totransition from the connected state 330 to the inactive state 332.Although described with respect to the inactive state 332, this step mayalternatively involve transitioning to any second resource control statethat is not supported by a second core-network type 404.

At 506, the UE performs a cell-selection procedure that selects a secondbase station. For example, the UE 110 performs the cell-selectionprocedure, which selects the base station 124. Continuing with the aboveexample, the cell-selection procedure is performed while the UE 110 isin the inactive state 332.

At 508, the UE processes system information received from the secondbase station to determine that the second base station supports a secondcore-network type. For example, UE 110 processes the system information436 to determine that the base station 124 supports the secondcore-network type 404. The system information 436 is received from thebase station 124, as shown at 435 in FIG. 4.

At 510, the UE determines that the second core-network type is differentfrom the first core-network type. For example, the UE 110 determinesthat the second core-network type 404 is different from the firstcore-network type 402. In particular, this can include determining thatat least one difference between the first core-network type 402 and thesecond core-network type 404 is such that a connection-resume procedurewith the second base station 124 may fail. In an example, determiningthat the second core-network type 404 is different from the firstcore-network type 402 includes determining that the second core-networktype 404 and first core-network type 402 support different resourcecontrol states and/or different connection procedures. The UE 110 makesthis determination based on system information 436 that is provided bythe first base station 120 (e.g., the base station 121 or the basestation 122) and the second base station 124.

As an example, the second core-network type 404 includes the EPC 160 andthe first core-network type 402 includes the 5GC 150. Unlike the 5GC150, the EPC 160 does not support the UE 110 in an inactive state 332and does not support a connection-resume procedure that enables the UE110 to transition from the inactive state 332 to the connected state330. Therefore, the UE 110 determines that the second core-network type404 is different from the first core-network type 402.

At 512, the UE detects a trigger that initiates a connection-resumeprocedure. For example, the UE 110 detects at least one of the followingtypes of triggers: an expiration of a timer 446 that directs the UE 110to perform the connection-resume procedure, a request to perform an RNAupdate 447, or a message 448 from the upper layer that directs the UE110 to perform the connection-resume procedure, as described above withrespect to FIG. 4. To avoid performing a connection-resume procedurewith the second base station 124, which may fail due to the differencesbetween the core-network types (e.g., differences between the EPC 160and the 5GC 150), the UE 110 performs at least one of the operations at514-520 prior to or instead of performing the connection-resumeprocedure.

At 514, the UE releases the wireless connection to the network. Forexample, the UE 110 releases the wireless connection to the RAN 140 byperforming an RRC connection-release procedure. The UE 110 performs theRRC connection-release procedure with the first base station 122 or thesecond base station 124. This procedure causes the UE 110 to transitionfrom the inactive state 332 to an idle state, which is supported by theEPC 160. Upon entering the idle state, the UE 110 deletes a resume UEcontext (e.g., an inactive UE context), a related identity (e.g., aresume identity or RNA identity), a security context, and so forth. Ingeneral, this step transitions the UE 110 from a current state that isnot supported by the second core-network type 404 to a second state thatis supported by the second core-network type 404.

At 516, the UE performs a connection-establishment procedure with thesecond base station. For example, the UE 110 performs theconnection-establishment procedure with the base station 124 of FIG. 1or 3 instead of performing the requested connection-resume procedure.The connection-establishment procedure is a procedure that is supportedby the EPC 160, and therefore may succeed. If theconnection-establishment procedure fails, the UE 110 can proceed torelease the connection at 514 and enter the idle state.

At 518, the UE postpones the connection-resume procedure. For example,the UE 110 postpones the connection-resume procedure triggered at 512.This postponement provides an opportunity for the UE 110 to perform asecond cell-selection procedure. The UE 110 postpones theconnection-resume procedure based on a predetermined amount of time or atimer. After the specified amount of time, the UE 110 proceeds torelease the connection at 514, perform the connection-establishmentprocedure at 516, remain in the inactive state and send a message to anupper layer at 520, or perform a second cell-selection procedure at 506.In some cases, the UE 110 continues performing multiple cell-selectionprocedures 506 until a base station 120 is selected that supports thefirst core-network type 402 (e.g., the 5GC 150). In other cases, the UE110 keeps track of a timer or a total quantity of attempts and proceedsaccording to 514, 516, or 520 if a time limit or a maximum quantity ofattempts has been reached. In some cases, the UE 110 continuesperforming cell-selection procedures at a predetermined time interval.

At 520, the UE sends a message is sent to an upper layer. For example,the UE 110 sends a message from the RRC layer to a mobility managementlayer, such as a non-access stratum (NAS) layer. The message indicatesan intent or determination of the UE 110 to not perform theconnection-resume procedure. In this case, the UE 110 continues tooperate in the inactive state 332. In other cases, the UE 110 sends themessage in response to the release of the connection at 514 or theconnection-establishment procedure at 516.

CONCLUSION

Although techniques for handling an attempt to resume a wirelessconnection using a base station that supports a different core-networktype have been described in language specific to features and/ormethods, it is to be understood that the subject of the appended claimsis not necessarily limited to the specific features or methodsdescribed. Rather, the specific features and methods are disclosed asexample implementations of handling an attempt to resume a wirelessconnection using a base station that supports a different core-networktype.

1-15. (canceled)
 16. A method performed by a user equipment, the methodcomprising: establishing a wireless connection to a network using afirst base station that supports a first core-network type; suspendingthe wireless connection to the network; performing a firstcell-reselection procedure that selects a second base station;processing system information received from the second base station todetermine that the second base station supports a second core-networktype; determining that the second core-network type is different fromthe first core-network type; detecting a first trigger that initiates aconnection-resume procedure; and responsive to detecting the firsttrigger and determining that the second core-network type is different,performing, in place of initiating the connection-resume procedure, oneor more first operations comprising: (i) releasing the wirelessconnection to the network; (ii) performing a connection-establishmentprocedure with the second base station; (iii) performing a firstinstance of postponing the connection-resume procedure, the firstinstance of postponing the connection-resume procedure comprising:initiating a first timer; and performing a second cell-reselectionprocedure responsive to an expiration of the first timer; or (iv)sending a message to an upper layer, the message indicating an intentnot to perform the connection-resume procedure.
 17. The method of claim16, wherein: the one or more first operations comprise performing thefirst instance of postponing the connection-resume procedure; and thefirst instance of postponing the connection-resume procedure furthercomprises: based on the second cell-reselection procedure, selecting athird base station that supports the first core-network type; andperforming the connection-resume procedure to resume the wirelessconnection to the network using the third base station.
 18. The methodof claim 16, further comprising: responsive to the secondcell-reselection procedure selecting a third base station that supportsa third core-network type that differs from the first core-network type,detecting a second trigger that initiates the connection-resumeprocedure; and responsive to detecting the second trigger, performingone or more second operations comprising: (i) releasing the wirelessconnection to the network; (ii) performing the connection-establishmentprocedure with the third base station; (iii) performing a secondinstance of postponing the connection-resume procedure, the secondinstance of postponing comprising: initiating the first timer; andperforming a third cell-reselection procedure responsive to anexpiration of the first timer; or (iv) sending the message to the upperlayer indicating the intent not to perform the connection-resumeprocedure.
 19. The method of claim 16, wherein the performing of the oneor more first operations comprises: releasing the wireless connection tothe network; and responsive to releasing the wireless connection to thenetwork, sending the message to the upper layer to further indicate thatthe wireless connection to the network was released instead ofperforming the connection-resume procedure.
 20. The method of claim 16,wherein the performing of the one or more first operations comprises:performing the connection-establishment procedure with the second basestation; and responsive to performing the connection-establishmentprocedure, sending the message to the upper layer.
 21. The method ofclaim 16, wherein the performing of the one or more first operationscomprises: sending the message to the upper layer by sending the messagefrom a radio-resource control layer to a mobility management layer. 22.The method of claim 16, wherein the first trigger comprises a request toperform a radio access-network notification-area update.
 23. The methodof claim 16, further comprising: operating the user equipment in a firstresource control state responsive to suspending the wireless connectionto the network, wherein: the first core-network type supports the firstresource control state; and the second core-network type does notsupport the first resource control state.
 24. The method of claim 23,wherein: the first resource control state comprises an inactive state.25. The method of claim 16, further comprising: responsive to suspendingthe wireless connection to the network, setting a second timer, whereinthe first trigger comprises an expiration of the second timer.
 26. Themethod of claim 25, further comprising: receiving a request message fromthe first base station, wherein the suspending of the wirelessconnection to the network comprises suspending the wireless connectionto the network responsive to receiving the request message.
 27. Themethod of claim 26, wherein: the request message specifies a duration ofthe second timer; and the setting of the second timer comprises settingthe second timer to expire based on the duration.
 28. A user equipmentcomprising: a radio-frequency transceiver; and a processor and memorysystem configured to cause the user equipment to: establish a wirelessconnection to a network using a first base station that supports a firstcore-network type; suspend the wireless connection to the network;perform a first cell-reselection procedure that selects a second basestation; process system information received from the second basestation to determine that the second base station supports a secondcore-network type; determine that the second core-network type isdifferent from the first core-network type; detect a first trigger toinitiate a connection-resume procedure; and responsive to detecting thefirst trigger and determining that the second core-network type isdifferent, perform, in place of initiating the connection-resumeprocedure, one or more operations comprising: (i) releasing the wirelessconnection to the network; (ii) performing a connection-establishmentprocedure with the second base station; (iii) initiating a first timerand performing a second cell-reselection procedure responsive to anexpiration of the first timer; or (iv) sending a message to an upperlayer, the message indicating an intent not to perform theconnection-resume procedure.
 29. The user equipment of claim 28,wherein: the first core-network type comprises a Fifth-Generation Corenetwork; and the second core-network type comprises an Evolved PacketCore network.
 30. The user equipment of claim 28, wherein the processorand memory system is further configured to cause the user equipment to:operate the user equipment in an inactive state responsive to suspendingthe wireless connection to the network, wherein: the first core-networktype supports the inactive state; and the second core-network type doesnot support the inactive state.
 31. The user equipment of claim 28,wherein: the one or more operations further comprises: initiating thefirst timer and performing the second cell-reselection procedureresponsive to the expiration of the first timer; and the processor andmemory system is further configured to cause the user equipment to:based on the second cell-reselection procedure, select a third basestation that supports the first core-network type; and perform theconnection-resume procedure to resume the wireless connection to thenetwork using the third base station.
 32. The user equipment of claim28, wherein the one or more operations comprises: releasing the wirelessconnection to the network; and sending the message to the upper layer,the message further indicating that the wireless connection to thenetwork was released.
 33. The user equipment of claim 28, wherein theone or more operations comprises: sending the message to the upperlayer, wherein the message is sent from a radio-resource control layerto a mobility management layer.
 34. The user equipment of claim 28,wherein the processor and memory system is further configured to causethe user equipment to: responsive to suspending the wireless connectionto the network, set a second timer, wherein the first trigger comprisesan expiration of the second timer.
 35. The user equipment of claim 34,wherein the processor and memory system is further configured to causethe user equipment to: receive a request message from the first basestation that specifies a duration of the second timer.